This invention relates to a process for placing appliques having markings such as white sidewalls, designs, letters, logos, trademarks, decals, even bar codes, etc. on a rubber substrate, which is given enhance stability by curing said appliques with or to the rubber substrate, preferably during the cured shaping of the substrate, such as a tire and said resulting product. Also, the applique can have scuff ribs molded therein. More particularly, this invention relates to a more economical method of making a tire, specifically a racing or airplane tire, having a precisely positioned applique being colored on the normal black or white sidewall to give a tire having clear colored precise demarcation lines to give a low defect or blemish tire and with scuff ribs to protect the applique. Also, this invention is useful for placing appliques on rubber hose, belts and other rubber products.
Another embodiment of this invention involves use of a specific mold having grooves therein to mold scuff ribs or bars at least beneath the surface of the cured applique on the cured tire.
White sidewall tires are very popular with car makers. Tires having other types of appliques on the sidewalls thereof, such as lettering, logos, decals, or bar codes and the like, are also very popular. However, the construction of tires having white sidewalls or decorative appliques on the sidewall thereof is a complicated procedure. It generally involves the coextrusion of a black sidewall rubber with a white sidewall rubber and laminating a protective cover strip over the white rubber to form a sidewall preassembly. This tire sidewall preassembly is then applied in sequence with the other required tire components to the tire building drum to form a green or uncured tire. The green tire is then typically cured in a tire press, with the desired applique being formed by the grooves in the tire mold. After the tire has been cured, it is carefully ground and buffed to expose the decorative applique which was previously covered and protected by the cover strip.
Coextrusion is a complicated process which involves the utilization of sophisticated equipment and a large number of profile dies. The grinding and buffing step which is required to remove the cover strip is also complicated and labor intensive. These additional steps which are required in building tires having decorative appliques on a sidewall thereof adds significantly to the cost of building the tire.
In conventional white sidewall tires, the white rubber component represents a very substantial portion of the sidewall. However, it is desirable for tires to have thin sidewalls in order to attain desired performance characteristics. Accordingly, the decorative applique on the sidewall of a tire should be as thin as possible. Nevertheless, certain production and performance criteria has limited the degree to which the thickness of sidewall applique can be reduced.
There are additional problems associated with tires having decorative applique on a sidewall thereof which are built using standard techniques. For instance, such tires have more blemishes, imperfections, and voids in the sidewall area as compared to black sidewall tires. Additionally, problems associated with the white sidewall splice opening sometimes also occur. Misalignment of the white sidewall preassembly relative to mold grooves is a frequently encountered problem which leads to blemished tires. The grinding procedure used in building standard tires having decorative appliques on a sidewall thereof sometimes leads to the formation of surface crack sites.
For the aforementioned reasons, tire having decorative appliques on a sidewall thereof and the conventional procedures used in building such tires leave much to be desired. To obviate these shortcomings associated with standard techniques for building tires having decorative appliques on a sidewall thereof, it has been proposed to replace the previously known sidewall decorative features with appliques which are painted on to conventional black wall tires. However, painting designs on to the sidewall of tires has not proven to be a satisfactory answer to the problem. This is largely due to the fact that designs which are painted on are quite thin and can be easily damaged by scraping, scuffing and the like.
The concept of applying premolded tire sidewall appliques to standard black wall tires has also been proposed. Difficulties have been encountered with maintaining adequate adhesion between the sidewall applique and the tire. Also, tires made utilizing such techniques typically have inferior scuff resistance such that the applique fails at the interface.
Over a dozen years ago Hayakama, et al issued U.S. Pat. No. 4,252,589 assigned to Bridgestone Tire Company, Limited, that set forth the prior art problems of making appliques containing tires as applied to automatic tire building operations and specifically summarizes the inoperatability in three numbered statements. Then, Hayakama, et al. provided a solution that required the thin rubber sheets to be a partially vulcanized rubber sheets having 50-80% vulcanization degree that was further vulcanized.
Another problem associated with providing appliques with cured molded rubber products, viz, tires, is the applique tends to be abraded in use to leave the applique disfigured with an unattractive appearance.
In general, the tire without an applique is produced on the conventional tire building drum or cylindrical former by assembling the parts or plies, whether bias or radial one, to leave the green tire case thereon. Then, the green tire case is placed in a mold, inflated and cured at about 250xc2x0 F. to 450xc2x0 F. for about 15 to about 45 minutes to give a standard black tire.
In this invention the applique preferably is applied while the green tire case is still on the drum and when the tire is a radial one, it is preferred to apply the applique to the green tire case while the drum is extended to at least partial inflate or expand the case in tread area to cause the sidewalls to slope toward the tread from the bead. The applique includes a film carrier having a rubberized ink design, decal, letters, symbols, related design pattern, or bar code printed thereon or to give a pleasing message. A thin gauge non-staining rubber backing is laminated to the message side of said film to give a laminate. The lamination is preferably accomplished by passing the film with the thin gauge non-staining rubber backing through a pinch roll or similar pressure means to cause the film and backing to adhere to each other sufficient to withstand the curing step for the tire.
A green tire case is built on a tire drum by the tire builder assembling the various parts such as plies, i.e., tread and sidewalls with the desired reinforcing such as steel, polyester, polyamide, etc. cords or wires with the beads in place.
Then preferably with the drum activated to cause the tread section of the case to move outward to give the sidewalls a slope to the beads, the applique is precisely positioned on the green tire case. It is preferred to use the component lights on the tire building drum to indicate the position on the green tire case where the tire builder is to locate the applique. The adjustable component lights project on the green tire case in a vertical and horizontal plane to form a point or place to locate the applique. Preferably, the applique has a mark such as a small v-marking center of the applique to facilitate indicating where the applique is placed relative to point of light. Then the applique with the v-mark, for instance, and light in coincident is spread on the case as shown in the drawings and stitched down.
With the applique laminate located and stitched to the green tire case, the green tire case is removed from the building drum and placed in a toroid mold to be inflated by pressurizing the mold bladder and cured at usually cure conditions, for instance, about 250 to 400xc2x0 F. for about 15 to about 60 minutes depending on curative in the tire case rubber.
When the cured tire is removed from the mold, the applique has clear, crisp pattern lines and is precisely located on the tire to advantageously show the visual message for instance, a bar code or brand, on the tire. Also, this method gives letters with sharp edges and excellent half tones with freedom from filled in bars or space in letters such as xe2x80x9cA, D, O. and Rxe2x80x9d. The rubberized ink applique has great durability and resistance to curbing. These tires with appliques, for instance the trademark letters of the manufacture, can be made cheaper by applying the appliques to the green tire case before placing the green tire case in the mold. Lettered tires made according to this invention can be readily seen on a racing or airplane tire and affords great visibility on tires and permits their advertising and identification to those viewing the tires.
Also, it was discovered that the inside surface of the mold could have engraved grooves of scuff ribs or bars therein, preferably partially circumferentially inside the wall, to give a cured rubber article whose applique could be abraded, preferably in use, to give a pleasing appearance primarily due to location of the scuff bars under the applique.
For instance, a racing tire receives harsh treatment in handling in the pits where the tire is dragged or pushed over the surface such as concrete of the pit. This action causes the applique letters and design to be abraded or scuffed away to produce an unsightly appearing appliques. By placing a series of small scuff ribs beneath the applique, it was unexpectedly discovered that the destruction of the appearance was limited and, in some cases, could even be enhanced. For instance, the letters or design over the scuff ribs or bars can be removed by scuffing to give an internal curve appearance which some on viewing refers to as a racy effect or tends to give the appearance the tire is going faster. This is an unobvious effect not expected from curved ribs essentially 0.1 to 0.015 inches in height and an arc length 0.05 to 0.07 inches at the surface. It is found that the ribs should preferably be about 0.3 to 0.4 inches apart.
Further, it was discovered that the grooves could be placed inside the tire surface essentially entirely around the 360xc2x0 surface. Further it was amazing to discover the ribs produced in the tire sidewall was not offensive or destructive to the appearance of the freshly molded tire. This discovery lets the tire molder place the green tire in mold without having to worry about where the applique is located in the mold or that a blemish will be caused in the finished tire.